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Automated probe accuracy testing

probe_accuracy_test_suite.py is a collection of tests to help checking probe accuracy, precision and drift under different conditions.

Default Tests Included

  • 1 test, 30 samples at each bed mesh corners - check if there are issues with individual z drives.
  • 20 tests, 10 samples at bed center - check consistency within normal measurements
  • 1 test, 100 samples at bed center - check for drift

Changelog

I'm making updates as I receive feedback from the community on what tests are actually useful

  • 2022-06-09: Allow passing probe_accuracy parameters and generating statistics on repeatability tests

Installation

On your printer:

curl -sSL https://raw.githubusercontent.com/sporkus/probe_accuracy_tests/master/install.sh | bash

will clone/pull this repo and install the necessary python packages.

How to

Use python3 ~/probe_accuracy_tests/probe_accuracy_test_suite.py --help to see all the options.

Tests

  • Run all three tests: python3 ~/probe_accuracy_tests/probe_accuracy_test_suite.py
  • Enable tests individually with --corner/-c, --repeatability/-r, --drift/-d
  • Test parameters can be further specified:
    • corner test, 10 samples each: --corner 10
    • 5 Repeatability tests: --repeat 5
    • 50 probe samples drift test: --drift 50

Other options

  • add --speedtest to test a range of z-probe speed. Speed parameters are entered in interactive menu.
  • add --force_dock to force probe docking between tests to check docking issues.
  • add --export_csv to export data as csv.
  • add --speed/-retract for probe speed/retract distance override.
  • add --keep_first to force keeping first probe sample even if it's configured to be dropped normally.
  • add -output_dir/-o to change the output directory. Use this to save the graphs to a place easily accessible to you.

Requirements

Python

See requirements.txt

They will installed by installation script above. If they are not installed - they can be installed like this manually.

pip3 install -r requirements.txt

Printer

  • Need klicky macros properly configured, so that homing/leveling/probe accuracy gcodes will pick up the probe safely.
  • There was an issue that prevented running PROBE_ACCURACY near the front of the bed in klicky-macros.cfg. This was fixed on 2022/05/30. Please update your config file if you see this error msg: Must perform PROBE_ACCURACY with the probe above the BED!" .

Output

All graphs and data are saved to /tmp. Enable csv export with --export_csv flag.

Plot examples:

Terminal:

Interpreting results

  • The green area is the middle 50% range of your samples. The narrower this band is, the more precise your probe is.
  • The red area falls outside of median +-0.005mm. If you have a lot of samples in the red area, you MAY have issue (but not necessarily).
  • Graphs are fancy and helpful to find glaring issues, but it is unnecessary to chase the most perfect graphs.
  • If your repeatability range is 0.1mm or less, it should be sufficient to produce a good bed mesh. Increasing probe sample count (set in printer.cfg > [probe] > samples) can help sometimes.

Common Issues

  • Getting probe sample exceeding samples_tolerance error? Try increasing [probe]:sample_tolerance to 0.02. This has no effect on the actual accuracy of your probe.
  • On Voron V2 printers, the most common issue is loose z-belts. An example from a printer with loose belt will look like the below image: